The present invention relates to methods and apparatus for encoding data into the vertical interval signals of a plurality of security television cameras so that the data may be used to intelligently determine which security camera pictures should be stored, and possibly retrieved. In the preferred embodiment of the invention, the pictures are stored in digital format on the disk drive of a computer system. The invention includes methods and apparatus for storing data from multiple security cameras, even though the vertical interval signals of the various cameras are in general not synchronized with respect to one another. In general, data inserted into the vertical interval signals will change field-by-field, so that the contents of registers where the data is stored must also be updated field by field. To avoid conflicts, the register updating operation must be performed only during vertical intervals associated with each camera.
This problem is solved in the preferred embodiment. Data to be inserted into the vertical interval signals of one or more television cameras is digitally phase controlled and locked to a particular horizontal line occurring after the start of vertical synchronization and read by a similar digitally phase controlled receiver locked to the same horizontal line.
The horizontal scan lines occurring within the vertical interval signals of television systems are increasingly used to transmit various kinds of data. For example, teletext and captioning for the deaf is usually transmitted on selected horizontal lines which occur during the vertical interval of a broadcast television signal. Also, the vertical interval signals of a scrambled television signal can be used to transmit appropriate instructions for enabling an authorized receiver to unscramble the signal.
In a typical security television system, signals from several television cameras are routed by cable or other means to some central location where they may be viewed and recorded on video tape. Scenes from different cameras are typically sequenced or multiplexed into one video signal for recording. This technique provides a still picture about once every four seconds for a single camera, and once every 40 seconds for ten cameras, and so forth. Time lapse video recorders can record ten to twenty days of such information on a single tape.
Since security television cameras typically monitor doors, hallways, and loading docks, hours, days and even months of the same scene will be recorded by existing systems. It will then require hours, days or even months to review all of the scenes recorded for a given location to locate the record of an intruder or other security-related event. Once the investigator notes suspicious activity, he must somehow identify the exact location of the scene on the tape in order to rapidly find it again. This may be crucial if the picture is used in a criminal prosecution. Typical security video tapes may have 50 to 100 scenes scattered throughout the tape. The time window for suspected activity may cover several tapes. If cameras feeding the recorder are located in different cities or states, the identification problem becomes practically impossible to solve.
The multiplexing of data onto television signals is known in the art. For example, U.S. Pat. No. 5,508,736 by Cooper, describes a system which combines television camera video and data from sensors at the camera location, and which transmits the composite signal to a recording device at another location. However, Cooper does not resolve the problem of receiving and storing data encoded into the video signals of a plurality of cameras, particularly cameras which are sending data asynchronously with each other. Also, Cooper does not provide a means to transmit data from the recording device to the camera location to respond to conditions signaled by the received data.
U.S. Pat. No. 4,831,438 by Bellman Jr., et al., discloses the transmission of data multiplexed with video signals from a plurality of cameras and sensors to another location for display and recording. However, Bellman, Jr., et al. use microwave and VHF radio as the transmissions means, and they encode data by generating a base band video signal and audio subcarriers instead of inserting the data into unused horizontal lines in the vertical interval. Bellman, Jr., et al. also disclose the reverse transmission of command signals from the receiving end into the camera and sensor elements. However, they do not address the problem of receiving and storing data sent asynchronously by remote cameras and sensors, nor do they provide for automatic detection of alarm conditions, the automatic storage of pictures and data responsive to alarm conditions, or the selective retrieval of stored pictures.
Accordingly, I intend my invention to provide an improved method for encoding data into the vertical interval of a plurality of security television cameras such that the data may be utilized to intelligently determine which pictures should be stored, and further, for storing selected pictures in a digital format in a computer system.
Another object of my invention is to build a system that will allow security systems to respond to the detection of suspicious activity, such as by moving the view of a camera or turning on lights. An embodiment of my invention accomplishes this by reverse transmitting control signals to the security camera locations during the vertical interval.
Another object of the invention is to build a security system which will allow viewing and control of remote sites thought a computer network. Such a network may be local to the secured location, but it may generally be any computer network, even the Internet
Another object of the invention is to build a security system in which stored video pictures have date and time stamps, the accuracy of which is unimpeachable. This is accomplished by storing the date and time stamped video pictures in a database which is password protected. This goal is further accomplished by only allowing network connections to the computer where video pictures are stored if such remote systems have the same software as the computer where the pictures are stored. This prevents persons connecting to the network from remote locations from modifying the original picture if they do not have authorization to enter the database in which the pictures are stored.
Many modern security cameras have connections for additional sensors, such as sensors which detect door openings, motion, invalid access cards, and other anomalies. Another object of my invention is to take advantage of such camera features by sending commands to a remote camera to acquire additional information in response to signals from such sensors, such as by moving its view to a particular door, and then storing the acquired pictures as described above. All of this may be done by transmitting such commands during the vertical interval signals, while at the same time receiving and storing pictures from the same scene. A computer system used with my invention could also activate an alarm or call the police.